Such a lighting device, which is known from US 2005/0111234 A1, comprises a surface from which light is emitted to illuminate a room, for example. The light emitting surface of the lighting device is located at a front side of the lighting device. The lighting device comprises a shell and an optical reflector. A space between the shell and the optical reflector serves as an air channel. An air inlet aperture of the air channel is located near a socket of the lighting device whilst an air outlet aperture of the air channel is located at the front side of the lighting device. A ventilator unit is located between the air inlet aperture and the air outlet aperture for moving air from the air inlet aperture through the ventilator unit to the air outlet, which air dissipates the heat of the LED. The ventilator unit acts as a cooling unit. It is also possible to reverse the direction of air.
If such a lighting device is mounted in a ceiling or a luminaire which is closed at the back side of the lighting device, hardly any air flow will be possible. Furthermore, in the case that the flow of air is directed from the front side of the lighting device to the back side, the heated air will be exhausted above the ceiling or between the lighting device and the luminaire, thereby heating the space above the ceiling or between the lighting device and the luminaire, respectively.